Some open top vehicles are provided with detachable hard roofs to maximize the riding comfort of the vehicles according to the weather. However, in most vehicles, it is extremely difficult to find a space for stowing away the detached roof. When the vehicle is provided with a fixed front roof and a fixed rear roof defining a roof opening extending across the entire width of the roof, the detachable roof consists of a substantially planar member, but it still is difficult to find a space to accommodate the detached roof within the vehicle in most cases. Such a roof structure is often provided with a central bar member connecting the central parts of the front and rear roofs for added rigidity, and such a roof structure is called as a T-bar roof.
For passenger cars and recreational vehicles, sliding roofs are widely used, and an example of such a sliding roof is disclosed in copending United States Pat. application Ser. No. 159,082 filed Feb. 23, 1988. However, such sliding roofs cannot be applied to those open top vehicles where the roof opening extends substantially across the entire width of the roof because the guide rails must extend along either lateral side of the roof and thus seriously interfere with the open top roof structure. Japanese Pat. laid open publication No. 59-143719 discloses a sliding roof structure for a T-bar roof in which a guide rail for guiding a front part of the sliding roof extends along the bar member extending between the front and rear roofs and a pair of guide rails for guiding rear parts of the sliding roof extend along either side portion of the rear roof. However, according to this proposal, the possible travel distance of the sliding roof is limited by the length of the guide rails provided in the rear roof. In other words, the ratio of the roof opening area to the entire roof area is quite limited, and the comfort of an open top vehicle can be obtained only to a limited extent.